Publication Citation: IDENTIFYING THE FLUID-TO-SOLID TRANSITION IN CEMENTITIOUS MATERIALS AT EARLY AGES USING ULTRASONIC WAVE VELOCITY AND COMPUTER SIMULATION

NIST Authors in Bold

Author(s):

G Sant; Dale P. Bentz; W Weiss;

Title:

IDENTIFYING THE FLUID-TO-SOLID TRANSITION IN CEMENTITIOUS MATERIALS AT EARLY AGES USING ULTRASONIC WAVE VELOCITY AND COMPUTER SIMULATION

Published:

February 01, 2009

Abstract:

Assessing the fluid-to-solid transition in cementitious systems at early-ages is crucial for scheduling construction operations, determining when laboratory testing can begin, and for assessing when computer simulations of shrinkage stress should begin. This transition has been traditionally assessed using penetration techniques (e.g. the Vicat tests), which though easy to perform, do not directly relate to the evolution of fundamental material properties or the microstructure. This paper assesses the fluid-to-solid transition of a cementitious material at early ages using measures which relate to the formation of a solid-skeleton in the material. The increase in the ultrasonic wave velocity is correlated to the percolation of a solid structure which occurs during the fluid-to-solid transition. Results of computer modeling (using CEMHYD3D) indicate that solidification as determined from the percolation of the solids is similar to experimental observations (Vicat tests). It is noted that the rate of change in the pulse velocity is not a rigorous method for assessment of the time of solidification. Rather, an increase in the pulse velocity beyond a threshold value appears to be a more appropriate method to assess structure formation. Further, the isothermal conduction calorimetry response is observed to not correspond to a fundamental aspect related to solid percolation or structure formation in the material.

Conference:

American Concrete Institute Spring convention

Proceedings:

Transition from Fluid to Solid: Re-examining the Behavior of Concrete at Early Ages